An independent group with deep ties to the president's re-election campaign launched a television ad Tuesday hitting Mitt Romney's business practices at Bain Capital, just 24 hours after Obama's team debuted its own ad attacking the Republican presidential candidate's work at the private-equity firm.

By law, campaigns and the outside groups are forbidden from working with each other. But at times like this, the lines of separation seem blurred if not crossed.

"The idea that these groups are independent is a fiction in reality terms and, we believe, a fiction in legal terms," said Fred Wertheimer of Democracy 21, a campaign-finance-reform advocacy group.

The back-to-back Obama spots, to run in four of the same five general election swing states, are a sign of the new world of campaign finance, where so-called super political-action committees have wide leeway to spend as much as they want to help or hurt candidates. And the ads also cast new light on the cozy relationship between campaigns and these groups, raising questions about how independent they are from each other.

The coziness isn't limited to Democrats. A Romney-aligned super PAC is keeping him competitive on TV as he regroups for the general election. And the relationship between that group -- Restore Our Future -- and the presumptive GOP nominee was on vivid display during the Republican primaries, when the group spent $36 million on ads assailing the former Massachusetts governor's rivals.

Super PACs, born of a 2010 Supreme Court decision easing political spending rules, can raise and spend unlimited donations as long as they don't coordinate directly with the campaigns they support. But the lines are often blurry: The pro-Obama super PAC Priorities USA Action is run by former Obama White House aides, while Restore Our Future is staffed by former Romney advisers.

Strategists for the super PACs insist they are operating independently and are not relying on signals from the presidential campaigns as to what advertising strategy to pursue. But campaign-finance watchdogs are crying foul, arguing that super PACs have effectively become high-dollar shadow campaign operations for candidates otherwise constrained by much stricter federal campaign finance rules.

Said Wertheimer: "Candidate-specific super PACs are simply arms of the presidential campaigns and need to be treated as such and be subject to contribution limits."

Republicans have generally welcomed the emergence of super PACs, and several GOP-leaning groups spent millions to take control of the House and pick up six Senate seats in 2010. Obama sharply criticized the emergence of super PACs that year but ultimately green-lighted contributions to Priorities USA Action after it became clear that his campaign and other Democrats would be vastly outgunned otherwise.

Tuesday's new ad launched by Priorities USA Action highlights the failure of GST Steel, a Kansas City, Mo.-based company purchased by Bain Capital that went bankrupt and laid off 750 workers in 2001. A day earlier, the Obama campaign announced it was targeting Bain's management of GST Steel in a two-minute ad.

Priorities USA Action is spending $4 million to air the new ad, while the Obama campaign committed just under $100,000 to run its commercial. But Bill Burton, a former Obama White House aide who now heads Priorities USA Action, said the timing of the two ads was a coincidence and his group had not waited for the Obama campaign go after Bain before making a similar attack.

"It wasn't a matter of waiting for anything, this was our strategy," Burton said, adding that the ad had been shot in February and the group has several more it plans to air related to Bain.

Priorities USA has spent $2.7 million on ads in May, compared with $28.6 million by the Obama campaign, according to data provided by ad buyers.

Republican-leaning groups, by contrast, spent about $14 million on commercials in the same period. About $4.3 million was spent by Restore Our Future.